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News, 30 June 2011

X-ray flashes revised

Thanks to recent developments, the design parameters of the European XFEL’s X-ray flashes can be improved. This will tune the light even more to the future users’ needs.

You don’t build a complex facility like the European XFEL in a weekend. Digging the intricate tunnel system and building the world’s best electron accelerator just takes time. But this time has been used wisely to react to new developments.

Experience with the LCLS X-ray free-electron laser at SLAC National Accelerator Laboratory in California and results of the PITZ results of the Photoinjector Testfacility at DESY in Zeuthen have shown that a much better electron beam quality can be achieved at the European XFEL than previously assumed.

This has resulted in an updated undulator layout for the European XFEL, which has been published in a technical report recently. With the new parameters, the needs of future users can be met even better. These requirements had been collected and analysed in eight workshops over the last years.

In detail

The following list summarizes the most important changes:

  • Extending the photon energy range from 260 electron volts (eV) to 25 000 eV and the corresponding wavelengths from 0.05 nanometres (nm) to 4.6 nm. The previously specified ranges were 800 eV to 12 400 eV and 0.1 nm to 1.6 nm, respectively.
  • Providing X-ray pulses of variable duration from a few femtoseconds (fs) to about 100 fs, instead of about 100 fs only.
  • Modifying the magnetic design of undulators SASE 1 and SASE 2 such that the same extended energy range and the possibility to vary the X-ray energy can be provided for all hard X-ray instruments.
  • Defining three electron accelerator energies (10.5 GeV, 14 GeV, and 17.5 GeV) to enable the extended range of photon energies. These photon energy ranges overlap to a large extent. This facilitates the user operation of the European XFEL facility, since a large fraction of photon energies can be delivered in each electron beam mode by adjusting the gap of the undulators. At the same time, the beam properties at very soft and very hard X-ray energies can be improved using these three electron energy settings.
Photon energy range of SASE 1, SASE 2, and SASE 3 undulators for the three electron beam working points (10.5 GeV, 14 GeV, and 17.5 GeV). The ranges overlap to a large extent, thus facilitating the user operation of the European XFEL facility.